Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a first embodiment of a display screen or portion thereof with a graphical user interface;

FIG. 2 is a front view of a second embodiment of a display screen or portion thereof with a graphical user interface;

FIG. 3 is a front view of a third embodiment of a display screen or portion thereof with a graphical user interface; and,

FIG. 4 is a front view of a fourth embodiment of a display screen or portion thereof with a graphical user interface.

The broken lines of uneven length show the display screen and form no part of the claimed design. The remaining broken lines show portions of the graphical user interface that form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 